Fusion of MRI and sonography image for breast cancer evaluation using real-time virtual sonography with magnetic navigation: first experience

Evaluation of the intramammary distribution of breast lesions detected by MRI but not conventional second-look B-mode ultrasound using an MRI/ultrasound fusion technique

The objective of this study was to evaluate the intramammary distribution of MRI-detected mass and focus lesions that were difficult to identify with conventional B-mode ultrasound (US) alone. Consecutive patients with lesions detected with MRI but not second-look conventional B-mode US were enrolled between May 2015 and June 2023. Following an additional supine MRI examination, we performed third-look US using real-time virtual sonography (RVS), an MRI/US image fusion technique. We divided the distribution of MRI-detected mammary gland lesions as follows: center of the mammary gland versus other (superficial fascia, deep fascia, and atrophic mammary gland). We were able to detect 27 (84%) of 32 MRI-detected lesions using third-look US with RVS. Of these 27 lesions, 5 (19%) were in the center of the mammary gland and 22 (81%) were located in other areas. We were able to biopsy all 27 lesions; 8 (30%) were malignant and 19 (70%) were benign. Histopathologically, three malignant lesions were invasive ductal carcinoma (IDC; luminal A), one was IDC (luminal B), and four were ductal carcinoma in situ (low-grade). Malignant lesions were found in all areas. During this study period, 132 MRI-detected lesions were identified and 43 (33%) were located in the center of the mammary gland and 87 (64%) were in other areas. Also, we were able to detect 105 of 137 MRI-detected lesions by second-look conventional-B mode US and 38 (36%) were located in the center of the mammary gland and 67 (64%) were in other areas. In this study, 81% of the lesions identified using third-look US with RVS and 64% lesions detected by second-look conventional-B mode US were located outside the center of the mammary gland. We consider that adequate attention should be paid to the whole mammary gland when we perform third-look US using MRI/US fusion technique.

A review of MRI (CT)/US fusion imaging in treatment of breast cancer

The ultrasound fusion imaging system is a diagnostic device developed in Japan that utilizes ultrasound and magnetic positioning/navigation. A position sensor with a probe reads spatial location information from a magnetic field generator and by synchronously displaying ultrasound images and magnetic resonance (MR)/computed tomography (CT) images in real time. Lesions that are difficult to observe via ultrasonography alone, such as non-mass enhancement, can be identified. Furthermore, lesions that are difficult to identify with ultrasound alone indicated for MRI-guided biopsy under the National Health Insurance Scheme can be identified using ultrasound fusion technology, thereby enabling tissue biopsy to be performed under ultrasound guidance. Using this ultrasound fusion technology, not only non-mass enhancement but also small lesions that are difficult to identify using ultrasound alone can be detected, thus ensuring that a more accurate preoperative imaging diagnosis is established, and leading to safer, more reassuring examinations and surgical procedures. In this paper, we outline the use of this ultrasound fusion technology and fusion techniques in the treatment of breast cancer.

Invasive lobular carcinoma of the breast detected with real-time virtual sonography: a case report

BACKGROUND

Invasive lobular carcinoma (ILC) sometimes presents with unique clinical, pathologic, and radiographic features. In this case report, we describe a patient with ILC, whose initial presentation consisted with symptoms secondary to bone-marrow dissemination. In addition, the breast primary was revealed only by magnetic resonance imaging (MRI) followed by real-time virtual sonography (RVS).

CASE PRESENTATION

A 51-year-old woman presented to our outpatient clinic with dyspnea on exertion. She had severe anemia (hemoglobin, 5.3 g/dL) and thrombocytopenia (platelet count, 31 × 10³/mL). Bone-marrow biopsy was performed to evaluate hematopoietic function. The pathologic diagnosis was bone-marrow carcinomatosis due to metastatic breast cancer. Initial mammography followed by ultrasonography (US) failed to detect the primary tumor. On MRI, a non-mass-enhancement lesion was observed. While second-look US also did not detect the lesion, it was clearly visualized with RVS. We were finally able to biopsy the breast lesion. The pathologic diagnosis was ILC positive for both estrogen receptor and progesterone receptor, with 1 + immunohistochemical staining for human epidermal growth factor receptor 2. This case of ILC was characterized by bone-marrow metastasis. Due to decreased cell adhesion, the risk of bone-marrow metastasis is higher in ILC than in invasive ductal carcinoma, the most prevalent type of breast cancer. Biopsy of the primary lesion, which was initially only detected with MRI, was successfully performed with clear visualization during RVS, which is based on the fusion of MRI and US images.

CONCLUSION

In this case report and literature review, we describe the unique clinical characteristics of ILC and a strategy for identifying primary lesions that are initially only visualized with MRI.

Ultrasound-Tomographic Image Fusion - A Novel Tool for Follow up After Acute Complicated Appendicitis

BACKGROUND

Computerized tomography (CT) is an integral part of the follow-up and decision-making process in complicated acute appendicitis (AA) treated non-operatively. However, repeated CT scans are costly and cause radiation exposure. Ultrasound-tomographic image fusion is a novel tool that integrates CT images to an Ultrasound (US) machine, thus allowing accurate assessment of the healing process compared to CT on presentation. In this study, we aimed to assess the feasibility of US-CT fusion as part of the management of appendicitis.

MATERIALS AND METHODS

We retrospectively collected data of consecutive patients with complicated AA managed non-operatively and followed up with US Fusion for clinical decision-making. Patients demographics, clinical data, and follow-up outcomes were extracted and analyzed.

RESULTS

Overall, 19 patients were included. An index Fusion US was conducted in 13 patients (68.4%) during admission, while the rest were performed as part of an ambulatory follow-up. Nine patients (47.3%) had more than 1 US Fusion performed as part of their follow-up, and 3 patients underwent a third US Fusion. Eventually, 5 patients (26.3%) underwent elective interval appendectomy based on the outcomes of the US Fusion, due to a non-resolution of imaging findings and ongoing symptoms. In 10 patients (52.6%), there was no evidence of an abscess in the repeated US Fusion, while in 3 patients (15.8%), it significantly diminished to less than 1 cm in diameter.

CONCLUSION

Ultrasound-tomographic image fusion is feasible and can play a significant role in the decision-making process for the management of complicated AA.

Prospective Evaluation of Ultrasound in a Novel Position with MRI Virtual Navigation for MRI-Detected Only Breast Lesions: A Pilot Study of a More Efficient and Economical Method

The aim of this study was to evaluate the clinical utility of ultrasound (US) with magnetic resonance imaging (MRI) virtual navigation in a novel prone position for MRI-detected incidental breast lesions. Between June 2016 and June 2020, 30 consecutive patients with 33 additional Breast Imaging Reporting and Data System (BI-RADS) category 4 or 5 lesions that were detected on MRI but occult on second-look US were enrolled in the study. All suspicious lesions were located in real-time US using MRI virtual navigation in the prone position and then followed by US-guided biopsy or surgical excision. Pathological results were taken as the standard of reference. The detection rate of US with MRI virtual navigation was calculated. The MRI features and pathological types of these lesions were analyzed. A total of 31 lesions were successfully located with real-time US with MRI virtual navigation and then US-guided biopsy or localization, and the detection rate was 93.9% (31/33). Twenty-seven (87.1%, 27/31) proved to be benign lesions and four (12.9%, 4/31) were malignant lesions at pathology. Of the 33 MRI-detected lesions, 31 (93.9%, 31/33) were non-mass enhancements and two (6.1%, 2/33) were masses. This study showed that real-time US with prone MRI virtual navigation is a novel efficient and economical method to improve the detection and US-guided biopsy rate of breast lesions that are detected solely on MRI.

Evaluation of an MRI/US fusion technique for the detection of non-mass enhancement of breast lesions detected by MRI yet occult on conventional B-mode second-look US

PURPOSE

The aim of this study was to verify the utility of second-look ultrasound (US) using real-time virtual sonography (RVS), a magnetic resonance imaging (MRI)/US fusion technique, in identifying MRI-detected breast lesions with non-mass enhancement (NME).

METHODS

Consecutive patients who had one or more NME lesions detected by MRI yet occult on the subsequent second-look US in conventional B (cB)-mode imaging were enrolled in the study between June 2015 and April 2020. Supine MRI of the lesions was performed and, using its data, second-look US using RVS was performed.

RESULTS

Twenty patients with 21 NME lesions were included. The overall median lesion size on prone MRI was 23 mm (range, 5-63 mm). Supine MRI identified all the 21 NME lesions, and second-look US using RVS successfully detected 18 (86%) of them. RVS-guided biopsy was performed for histopathological evaluation, showing that nine of the 18 lesions were benign and the other nine malignant. Of the nine malignant lesions, two (22%) were invasive cancer and seven (78%) were ductal carcinoma in situ. In four of five patients who underwent prone MRI for preoperative evaluation, the diagnosis was benign and surgery was conducted as originally planned. In the other patient, the diagnosis was malignant and contralateral breast-conserving surgery was added. Three (14%) of the 21 NME lesions had no RVS correlates and were judged to be benign after 24-month follow-up.

CONCLUSION

The results suggest that second-look US using RVS helps identify MRI-detected NME lesions that are occult on cB-mode second-look US.

Magnetic Resonance Imaging Images under Deep Learning in the Identification of Tuberculosis and Pneumonia

This work aimed to explore the application value of deep learning-based magnetic resonance imaging (MRI) images in the identification of tuberculosis and pneumonia, in order to provide a certain reference basis for clinical identification. In this study, 30 pulmonary tuberculosis patients and 27 pneumonia patients who were hospitalized were selected as the research objects, and they were divided into a pulmonary tuberculosis group and a pneumonia group. MRI examination based on noise reduction algorithms was used to observe and compare the signal-to-noise ratio (SNR) and carrier-to-noise ratio (CNR) of the images. In addition, the apparent diffusion coefficient (ADC) value for the diagnosis efficiency of lung parenchymal lesions was analyzed, and the best b value was selected. The results showed that the MRI image after denoising by the deep convolutional neural network (DCNN) algorithm was clearer, the edges of the lung tissue were regular, the inflammation signal was higher, and the SNR and CNR were better than before, which were 119.79 versus 83.43 and 12.59 versus 7.21, respectively. The accuracy of MRI based on a deep learning algorithm in the diagnosis of pulmonary tuberculosis and pneumonia was significantly improved (96.67% vs. 70%, 100% vs. 62.96%) (P < 0.05). With the increase in b value, the CNR and SNR of MRI images all showed a downward trend (P < 0.05). Therefore, it was found that the shadow of tuberculosis lesions under a specific sequence was higher than that of pneumonia in the process of identifying tuberculosis and pneumonia, which reflected the importance of deep learning MRI images in the differential diagnosis of tuberculosis and pneumonia, thereby providing reference basis for clinical follow-up diagnosis and treatment.

Multi-Bevel Needle Design Enabling Accurate Insertion in Biopsy for Cancer Diagnosis

OBJECTIVE

To obtain definitive cancer diagnosis for suspicious lesions, accurate needle deployment and adequate tissue sampling in needle biopsy are essential. However, the single-bevel needles in current biopsy devices often induce deflection during insertion, potentially causing lesion missampling/undersampling and cancer misdiagnosis. This study aims to reveal the biopsy needle design criteria enabling both low deflection and adequate tissue sampling.

METHODS

A novel model capable of predicting needle deflection and tissue deformation was first established to understand needle-tissue interaction with different needle tip geometries. Experiments of needle deflection and ex-vivo tissue biopsy were conducted for model validation.

RESULTS

The developed model showed a reasonably good prediction on the correlation of needle tip type vs. the resultant needle deflection and tissue sampling length. A new multi-bevel needle with the tissue separation point below the needle groove face has demonstrated to be an effective design with an 87% reduction in deflection magnitude and equivalently long tissue sampling length compared to the current single-bevel needle.

CONCLUSION

This study has revealed two critical design criteria for biopsy needles: 1) multiple bevel faces at the needle tip can generate forces to balance bending moments during insertion to enable a low needle deflection and 2) the tissue separation point should be below the needle groove face to ensure long tissue sampling length.

SIGNIFICANCE

The developed methodologies and findings in this study serve as proof-of-concept and can be utilized to investigate various biopsy procedures to improve cancer diagnostic accuracy as well as other procedures requiring accurate needle insertion.

Quantitative Evaluation of an Automated Cone-Based Breast Ultrasound Scanner for MRI-3D US Image Fusion

Breast cancer is one of the most diagnosed types of cancer worldwide. Volumetric ultrasound breast imaging, combined with MRI can improve lesion detection rate, reduce examination time, and improve lesion diagnosis. However, to our knowledge, there are no 3D US breast imaging systems available that facilitate 3D US - MRI image fusion. In this paper, a novel Automated Cone-based Breast Ultrasound System (ACBUS) is introduced. The system facilitates volumetric ultrasound acquisition of the breast in a prone position without deforming it by the US transducer. Quality of ACBUS images for reconstructions at different voxel sizes (0.25 and 0.50 mm isotropic) was compared to quality of the Automated Breast Volumetric Scanner (ABVS) (Siemens Ultrasound, Issaquah, WA, USA) in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and resolution using a custom made phantom. The ACBUS image data were registered to MRI image data utilizing surface matching and the registration accuracy was quantified using an internal marker. The technology was also evaluated in vivo. The phantom-based quantitative analysis demonstrated that ACBUS can deliver volumetric breast images with an image quality similar to the images delivered by a currently commercially available Siemens ABVS. We demonstrate on the phantom and in vivo that ACBUS enables adequate MRI-3D US fusion. To our conclusion, ACBUS might be a suitable candidate for a second-look breast US exam, patient follow-up, and US guided biopsy planning.

Transrectal Ultrasound MRI-Fusion Biopsy of Perirectal Mass

This case report describes the novel use of ultrasound-guided MRI-fusion biopsy to sample an extraluminal perirectal mass. This is a 64-year-old man with a history of pT3N2b mucinous adenocarcinoma of the right colon with metastatic disease to the mesocolic lymph nodes. Two years after initial resection he was found on restaging CT to have a mass measuring ∼4.0 × 4.8 cm superior to the seminal vesicles. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) showed a moderately FDG avid soft tissue mass interposed between the prostate and the rectum. Multiparametric MRI revealed a 6.2 × 4.6 × 2.8 cm heterogeneous lobulated T2 hyperintense mass with enhancement just superior to the seminal vesicles. This mass was unable to be viewed using sigmoidoscopy. Using UroNAV technology, we were able to biopsy the mass in the clinic setting. Biopsy was confirmed as recurrent mucinous adenocarcinoma.

MRI-detected breast lesions: clinical implications and evaluation based on MRI/ultrasonography fusion technology

Magnetic resonance imaging (MRI) is a highly sensitive imaging modality that frequently reveals additional breast lesions that are occult on mammography and ultrasonography (US) and are thus difficult to diagnose. It is important to investigate these MRI-detected suspicious lesions, which are associated with a fairly high rate of malignancy. In this review, we have discussed MRI/US fusion technology, a magnetic position tracking system that synchronizes real-time US and MRI to improve lesion detection and enables comparisons of MRI and US findings of the detected lesions. This combination increases the precision of second-look US. We hope that our review underscores the importance of understanding the US findings and histopathology of MRI-detected breast lesions, as this will enable radiologists to perform appropriate assessments.

Protocole d’IRM abrégée pour le diagnostic et le dépistage du cancer du sein

Le cancer du sein est le premier cancer féminin en France, et sa détection précoce est indispensable. L’IRM mammaire est un élément de choix dans son diagnostic mais présente des coûts directs et indirects élevés, notamment du fait de sa durée qui ralentit son utilisation plus large. Compte tenu de ses éléments, l’utilisation d’un protocole abrégé se développe pour pallier ces inconvénients. Les premières données de la littérature tendent à penser que cet examen plus rapide permet également une durée d’interprétation plus courte. De plus, la sensibilité et la spécificité de l’examen ne sont pas inférieures à celles du protocole complet. Cet article explique ce nouveau concept et son intérêt, le compare au protocole complet et évoque les perspectives futures et notamment à l’adjonction de séquences à haute résolution temporelle.

Efficacy of Second-Look Ultrasound with MR Coregistration for Evaluating Additional Enhancing Lesions of the Breast: Review of the Literature

Contrast enhanced magnetic resonance imaging (CE-MRI) has acquired a central role in the field of diagnosis and evaluation of breast cancer due to its high sensitivity; on the other hand, MRI has shown a variable specificity because of the wide overlap between the imaging features of benign and malignant lesions. Therefore, when an additional breast lesion is identified at CE-MRI, a second look with targeted US is generally performed because it provides additional information to further characterise the target lesion and makes it possible to perform US-guided biopsies which are costless and more comfortable for patients compared with MRI-guided ones. Nevertheless, there is not always a correspondence between CE-MR findings and targeted US due to several factors including different operator's experience and position of patients. A new technique has recently been developed in order to overcome these limitations: US with MR coregistration, which can synchronise a sonography image and the MR image with multiplanar reconstruction (MPR) of the same section in real time. The aim of our study is to review the literature concerning the second look performed with this emerging and promising technique, showing both advantages and limitations in comparison with conventional targeted US.

Impact of an abbreviated protocol for breast MRI in diagnostic accuracy

PURPOSE

We aimed to compare the diagnostic accuracy and interpretation time of an abbreviated protocol relative to the complete protocol of breast magnetic resonance imaging (MRI) with the use of breast imaging reporting and data system (BI-RADS). Between-reader and between-protocol variability for BI-RADS classification and influence of reader expertise on diagnostic accuracies were also evaluated.

METHODS

We conducted a retrospective reader study in 90 women who underwent breast MRI: 30 benign examinations (graded as American College of Radiology [ACR] 1 or 2), 30 examinations graded as ACR 3 and 30 examinations requiring a histologic proof (graded as ACR 4 or 5). Two radiologists independently reviewed the protocols. The reference standard was 24 months of imaging follow-up (66.6%, n=60), percutaneous biopsy at the 12th month imaging follow-up (5.5%, n=5), and breast surgery (27.9%, n=25). Analysis was done on a per-breast basis. There were 26 cancers in 168 breasts (15.1%) RESULTS: Interpretation time was higher for the complete protocol (mean difference: 84 s, 95% CI [67;101] for senior and 83 s, 95% CI [70;95] for junior reader; P < 0.001). The reliability of BI-RADS classification between both protocols was very good with intraclass correlation coefficient of 0.89 for junior reader and 0.98 for senior reader; the inter-reader reliability was 0.94 and 0.90 for the complete and abbreviated protocols, respectively. For senior reader, the abbreviated and complete protocols yielded 95.1% and 94.4% specificity and 100% sensitivity.

CONCLUSION

Our data provide corroborating evidence that abbreviated protocols decrease interpretation time without compromising sensitivity or specificity. There was a high level of concordance between the abbreviated and complete protocols and between the two readers.

Pre-Operative Planning Using Real-Time Virtual Sonography, an MRI/Ultrasound Image Fusion Technique, for Breast-Conserving Surgery in Patients with Non-Mass Enhancement on Breast MRI: A Preliminary Study

The purpose of this retrospective study was to evaluate the effect of pre-operative planning using real-time virtual sonography (RVS), a magnetic resonance imaging (MRI)/ultrasound (US) image fusion technique on breast-conserving surgery (BCS) in patients with non-mass enhancement (NME) on breast MRI. Between 2011 and 2015, we enrolled 12 consecutive patients who had lesions with NME that exceeded the US hypo-echoic area, in which it was particularly difficult to evaluate the tumor margin. During pre-operative planning before breast-conserving surgery, RVS was used to delineate the enhancing area on the breast surface after additional supine breast MRI was performed. We analyzed both the surgical margin positivity rate and the re-operation rate. All NME lesions corresponded to the index cancer. In all patients, the diameter of the NME lesion was greater than that of the hypo-echoic lesion. The median diameters of the NME and hypo-echoic lesions were 24 mm (range: 12-39 mm) and 8.0 mm (range: 4.9-18 mm), respectively (p = 0.0002). After RVS-derived skin marking was performed on the surface of the affected breast, lumpectomy and quadrantectomy were conducted in 7 and 5 patients, respectively. The surgical margins were negative in 10 (83%) patients. Two patients with positive margins were found to have ductal carcinoma in situ in 1 duct each, 2.4 and 3.2 mm from the resection margin, respectively. None of the patients required additional resection. Although further prospective studies are required, the findings of our preliminary study suggest that it is very well possible that the use of RVS-derived skin marking during pre-operative planning for BCS in patients with NME would have resulted in surgical outcomes similar to or better than those obtained without the use of such marking.

Ultrasound Imaging Technologies for Breast Cancer Detection and Management: A Review

Ultrasound imaging is a commonly used modality for breast cancer detection and diagnosis. In this review, we summarize ultrasound imaging technologies and their clinical applications for the management of breast cancer patients. The technologies include ultrasound elastography, contrast-enhanced ultrasound, 3-D ultrasound, automatic breast ultrasound and computer-aided detection of breast ultrasound. We summarize the study results seen in the literature and discuss their future directions. We also provide a review of ultrasound-guided, breast biopsy and the fusion of ultrasound with other imaging modalities, especially magnetic resonance imaging (MRI). For comparison, we also discuss the diagnostic performance of mammography, MRI, positron emission tomography and computed tomography for breast cancer diagnosis at the end of this review. New ultrasound imaging techniques, ultrasound-guided biopsy and the fusion of ultrasound with other modalities provide important tools for the management of breast patients.

Second-look US Using Real-time Virtual Sonography, a Coordinated Breast US and MRI System with Electromagnetic Tracking Technology: A Pilot Study

Our aim was to retrospectively evaluate the utility of second-look ultrasound (US) using real-time virtual sonography (RVS) for detection of conventional B-mode (cB-mode) occult magnetic resonance imaging (MRI)-detected breast lesions. Between July 2011 and May 2015, 53 consecutive patients who underwent second-look US to identify lesions detected by prone MRI were enrolled in this study. Second-look US using RVS was performed for cB-mode occult MRI-detected breast lesions after an additional supine MRI. In the 53 patients, 59 lesions were initially detected by prone MRI, followed by second-look US. Of the 59 lesions, 20 (34%) were identified by second-look US using cB-mode. Of the 39 (66%) cB-mode occult lesions, 38 (97%) were detected in supine MRI and 33 (85%) were detected by second-look US using RVS. MRI morphology types of the 33 lesions were as follows: mass, 16; non-mass enhancement, 5; and focus, 12. US-guided biopsy under RVS or excisional biopsy demonstrated that of the 33 lesions, 8 (24%) were malignant and the remaining 25 (76%) were benign. A total of 53 (90%) MRI-detected lesions were sonographically identified using both cB-mode and RVS (p < 0.001). All five remaining US-occult lesions could be followed up under RVS after the enhancing area was marked on the breast surface using RVS. Although further prospective studies are required, the findings of our pilot study suggest that second-look US using RVS with additional supine MRI may improve the sonographic and histopathologic detection rate of cB-mode occult MRI-detected breast lesions.

Clinical Value of Real-Time Ultrasonography-MRI Fusion Imaging for Second-Look Examination in Preoperative Breast Cancer Patients: Additional Lesion Detection and Treatment Planning

BACKGROUND

This study was conducted to evaluate the clinical effect of real-time magnetic resonance imaging (MRI)-navigated ultrasonography (US) for preoperative second-look examination in patients with breast cancer.

PATIENTS AND METHODS

Between October 2013 and February 2015, 232 patients with breast cancer underwent MRI for staging; second-look US was performed in 70 patients to evaluate additional lesions suspected to be disease detected using MRI. We retrospectively included 67 lesions in 55 patients. Lesions were classified as detected on conventional US (group 1), and not visible on conventional US, but detected on MRI-navigated US (group 2). The imaging features between groups 1 and 2 were compared using Student t, χ², or Fisher exact tests. We compared the detection rate and histopathology of additional lesions using a McNemar test.

RESULTS

Heterogeneous background echotexture (69.6% [16 of 23] vs. 34.1% [14 of 41]) and lesion isoechogenicity (65.2% [15 of 23] vs. 7.3% [3 of 41]) on US and middle or posterior lesion depth on MRI (78.3% [18 of 23] vs. 46.3% [19 of 41]) were more common in group 2 (P < .05). More lesions were detected using MRI-navigated US (64 of 67; 95.5%) than conventional US (41 of 67; 61.2%; P < .01). Using MRI-navigated US we found more high-risk or malignant lesions than conventional US (21 vs. 11; P < .01). The optimal treatment plan was determined for 9 of 16 (56.3%) patients by virtue of MRI-navigated US.

CONCLUSION

Real-time MRI-navigated US significantly improved the detection of additional high-risk or malignant lesions during second-look US in preoperative evaluation of patients with breast cancer and ultimately determined the optimal treatment plan.

Endorectal fusion imaging: A description of a new technique

BACKGROUND

Fusion imaging is an accepted method in abdominal imaging allowing a simultaneous display of reference imaging with a live ultrasound (US) investigation. For prostate cancer, promising results have been published for endorectal US (ERUS)-guided biopsy of suspicious lesions in magnetic resonance imaging (MRI). To our knowledge, no other indication for the fusion of ERUS with MRI has been reported so far.

METHODS

We report on three patients scheduled for ERUS due to anorectal fistulae after treatment (n = 2) or rectal carcinoma (n = 1), which were scheduled for real-time virtual onography (RVS), a method for the fusion of MRI imaging with US.

RESULTS

In all patients, RVS was successful. The course of the fistulae could be defined and the success of the treatment could be confirmed. In the patient with rectal carcinoma, the lymph nodes suspicious in MRI could be identified.

CONCLUSIONS

MRI/ERUS fusion has the potential for follow-up of anorectal fistulae and abscesses, and staging of anal and rectal tumors.

Real-Time MRI Navigated Ultrasound for Preoperative Tumor Evaluation in Breast Cancer Patients: Technique and Clinical Implementation

Real-time magnetic resonance imaging (MRI) navigated ultrasound is an image fusion technique to display the results of both MRI and ultrasonography on the same monitor. This system is a promising technique to improve lesion detection and analysis, to maximize advantages of each imaging modality, and to compensate the disadvantages of both MRI and ultrasound. In evaluating breast cancer stage preoperatively, MRI and ultrasound are the most representative imaging modalities. However, sometimes difficulties arise in interpreting and correlating the radiological features between these two different modalities. This pictorial essay demonstrates the technical principles of the real-time MRI navigated ultrasound, and clinical implementation of the system in preoperative evaluation of tumor extent, multiplicity, and nodal status in breast cancer patients.

Real-time virtual sonography examination and biopsy for suspicious breast lesions identified on MRI alone

OBJECTIVES

The purpose of our study was to assess whether there is a potential additional value of real-time virtual sonography (RVS) to second-look ultrasound (US) examination and biopsy for breast lesions identified on MRI alone.

METHODS

A retrospective review of the records of 70 consecutive patients (78 lesions) with breast abnormalities identified on MRI alone was performed. All suspicious enhancing lesions were subsequently evaluated with second-look US. Lesions not observed on second-look US underwent RVS. Pathological findings were confirmed by subsequent percutaneous biopsy or excision.

RESULTS

Of the 78 MRI-detected lesions, second-look US correlation was made in 50 (64 %), including 22 malignant and 28 benign lesions. The remaining 28 lesions (36 %) were scheduled to undergo RVS. Four lesions were not visible on the second breast MRI. The remaining 24 lesions were RVS correlated and underwent RVS-guided biopsy; these included seven malignant and 17 benign lesions. Overall, 74 of 74 (100 %) true MRI-detected lesions were confirmed by histological results without using MRI-guided breast biopsy. The cancer rate was 29 %.

CONCLUSIONS

RVS can increase the sonographic detection and biopsy rate of lesions identified on breast MRI alone.

KEY POINTS

• All 74 MRI-detected lesions were confirmed without using MRI-guided biopsy. • Four lesions were not visible on second breast MRI. • RVS can increase sonographic detection of lesions identified on breast MRI alone. • RVS-guided breast biopsy can be an alternative to MRI-guided biopsy.

Breast sentinel lymph node navigation with three-dimensional computed tomography-lymphography: a 12-year study

PURPOSE

To evaluate the utility of three-dimensional (3D) computed tomography (CT)-lymphography (LG) breast sentinel lymph node navigation in our institute.

PATIENTS AND METHODS

Between 2002 and 2013, we preoperatively identified sentinel lymph nodes (SLNs) in 576 clinically node-negative breast cancer patients with T1 and T2 breast cancer using 3D CT-LG method. SLN biopsy (SLNB) was performed in 557 of 576 patients using both the images of 3D CT-LG for guidance and the blue dye method.

RESULTS

Using 3D CT-LG, SLNs were visualized in 569 (99%) of 576 patients. Of 569 patients, both lymphatic draining ducts and SLNs from the peritumoral and periareolar areas were visualized in 549 (96%) patients. Only SLNs without lymphatic draining ducts were visualized in 20 patients. Drainage lymphatic pathways visualized with 3D CT-LG (549 cases) were classified into four patterns: single route/single SLN (355 cases, 65%), multiple routes/single SLN (59 cases, 11%) single route/multiple SLNs (62 cases, 11%) and multiple routes/multiple SLNs (73 cases, 13%). SLNs were detected in 556 (99.8%) of 557 patients during SLNB.

CONCLUSION

CT-LG is useful for preoperative visualization of SLNs and breast lymphatic draining routes. This preoperative method should contribute greatly to the easy detection of SLNs during SLNB.

Targeted sonography using an image fusion technique for evaluation of incidentally detected breast lesions on chest CT: a pilot study

BACKGROUND

With increasing use of computed tomography (CT), incidentally detected breast lesions are being encountered more frequently. The aim of our study was to verify the utility of targeted sonography using an image fusion technique, real-time virtual sonography (RVS) that coordinates real-time sonography images with previously obtained CT images using a magnetic position tracking system, for evaluation of incidentally detected breast lesions on chest CT.

METHODS

Eleven lesions in 11 women with no history of breast cancer who were referred to our unit for assessment of breast lesions incidentally detected on CT were enrolled in this study. To assess the efficacy of targeted sonography using RVS, we analyzed the frequency of sonographic detection of incidentally detected breast lesions and the difference between sonography- and CT-determined diameters.

RESULTS

Using RVS guidance, all 11 lesions were sonographically detected. Ten (91 %) of 11 lesions underwent sonography-guided biopsy, yielding a success rate of 90 % (9/10). The remaining sonography-guided biopsy failure lesion required surgical biopsy for definitive diagnosis; this was performed after RVS was used to mark CT imaging information onto the breast surface. Four (36 %) lesions subsequently proved to be malignant. The mean diameters provided by RVS were 14.9 ± 6.7 mm for sonography and 16.8 ± 7.5 mm for CT (p = 0.538).

CONCLUSION

Using RVS, a sonographic probe was precisely guided to the lesions. Our results suggest that targeted sonography using RVS is a useful technique for identifying incidentally detected breast lesions on chest CT.

Electromagnetic tracking in medicine--a review of technology, validation, and applications

Object tracking is a key enabling technology in the context of computer-assisted medical interventions. Allowing the continuous localization of medical instruments and patient anatomy, it is a prerequisite for providing instrument guidance to subsurface anatomical structures. The only widely used technique that enables real-time tracking of small objects without line-of-sight restrictions is electromagnetic (EM) tracking. While EM tracking has been the subject of many research efforts, clinical applications have been slow to emerge. The aim of this review paper is therefore to provide insight into the future potential and limitations of EM tracking for medical use. We describe the basic working principles of EM tracking systems, list the main sources of error, and summarize the published studies on tracking accuracy, precision and robustness along with the corresponding validation protocols proposed. State-of-the-art approaches to error compensation are also reviewed in depth. Finally, an overview of the clinical applications addressed with EM tracking is given. Throughout the paper, we report not only on scientific progress, but also provide a review on commercial systems. Given the continuous debate on the applicability of EM tracking in medicine, this paper provides a timely overview of the state-of-the-art in the field.

Prediction of prone-to-supine tumor displacement in the breast using patient position change: investigation with prone MRI and supine CT

BACKGROUND

One of the challenges for clinical use of preoperative breast magnetic resonance imaging (MRI) is how to transfer prone MRI information to the operating theater with a supine surgical position. The aim of this study was to retrospectively evaluate tumor displacement in the breast by changing the patient position from prone to supine (prone-to-supine tumor displacement), using preoperative prone MRI and supine computed tomography (CT).

METHODS

Preoperatively, 55 Japanese women with 57 breast cancer lesions underwent breast MRI in the prone position and breast CT in the supine position. Tumor positions in both the prone and supine positions were measured on X-, Y-, and Z-coordinates by fixing the nipple to the origin (0, 0, 0). As an indicator of the mobility of the breast, the ratio of the breast projection between the prone MRI and supine CT (prone-to-supine projection ratio) was calculated. The direction and distance of prone-to-supine tumor displacement was analyzed by dividing the breast into four quadrants according to the tumor position.

RESULTS

When changing the patient position from prone to supine, tumors located in the inner-upper and inner-lower quadrants tended to move radially toward the center of the nipple. The movement distance of the tumors in the inner-lower and outer-lower quadrants was very strongly correlated with the prone-to-supine breast projection ratio (r ≥ 0.8, p < 0.05). Conversely, in the outer-upper quadrant, the direction of tumor displacement was variable, and the distance of tumor displacement did not correlate with the prone-to-supine projection ratio.

CONCLUSIONS

The present study showed that prone-to-supine tumor displacement in the breast differs depending on tumor location. The inner-lower quadrant of the breast may be the most predictable area for prone-to-supine tumor displacement.

Reproducible surveillance breast ultrasound using an image fusion technique in a short-interval follow-up for BI-RADS 3 lesions: a pilot study

The aim of our study was to verify the utility of surveillance ultrasound (US) using real-time virtual sonography (RVS)--to coordinate present US images with past US images reconstructed from previously acquired US volume data using an image fusion technique--for short-interval follow-up of Breast Imaging-Reporting and Data System (BI-RADS) category 3 mass lesions. We enrolled 20 women (23 lesions) with more than 24 mo of follow-up after classification as BI-RADS category 3 during initial US. US surveillance was scheduled at 6, 12 and 24 mo. Measurement of the target lesion diameter was performed after the probe was adjusted to include the maximum diameter of a past US image at each visit. RVS was technically successful in 100% of patients. All target lesions were detected, including two iso-echoic lesions. The mean target lesion diameters at baseline and at 6, 12 and 24 mo were 8.2 ± 4.2, 8.4 ± 4.5, 8.1 ± 4.5 and 8.3 ± 5.0 mm, respectively (p = 0.785). Our results suggest that RVS is a reproducible, operator-independent technique for comparison of US images of BI-RADS category 3 mass lesions obtained at different time points.

Second-look US: how to find breast lesions with a suspicious MR imaging appearance

Breast magnetic resonance (MR) imaging has high sensitivity in breast cancer diagnosis. The probability of malignancy for additional detected lesions is higher in patients with breast cancer than in the population without malignancy, which is why biopsy or further study should be considered for additional detected lesions. Because of the shortcomings of MR imaging-guided biopsy, second-look ultrasonography (US) may be the preferred next step. Detecting target lesions at second-look US and correlating lesions between the two modalities may be challenging. Using axial MR imaging to localize the lesion with respect to the nipple and the lesion-to-nipple distance can narrow the scan range at US. Evaluating the lesion's location relative to the mammary zones and surrounding tissues, as well as noting its depth, characteristics, and nearby landmarks, will aid in lesion correlation. Doppler imaging, tissue harmonic imaging, and other US techniques can be used to identify subtle lesions. Although malignant breast lesions may appear probably benign at second-look US, decision making for biopsy must be based primarily on MR imaging findings. In sonographically occult, MR imaging-detected lesions with suspicious MR imaging features, the probability of malignancy is much higher than 2%, and MR imaging-guided biopsy must be performed.

Using surface markers for MRI guided breast conserving surgery: a feasibility survey

Breast MRI is frequently performed prior to breast conserving surgery in order to assess the location and extent of the lesion. Ideally, the surgeon should also be able to use the image information during surgery to guide the excision and this requires that the MR image is co-registered to conform to the patient's position on the operating table. Recent progress in MR imaging techniques has made it possible to obtain high quality images of the patient in the supine position which significantly reduces the complexity of the registration task. Surface markers placed on the breast during imaging can be located during surgery using an external tracking device and this information can be used to co-register the images to the patient. There remains the problem that in most clinical MR scanners the arm of the patient has to be placed parallel to the body whereas the arm is placed perpendicular to the patient during surgery. The aim of this study is to determine the accuracy of co-registration based on a surface marker approach and, in particular, to determine what effect the difference in a patient's arm position makes on the accuracy of tumour localization. Obtaining a second MRI of the patient where the patient's arm is perpendicular to body axes (operating room position) is not possible. Instead we obtain a secondary MRI scan where the patient's arm is above the patient's head to validate the registration. Five patients with enhancing lesions ranging from 1.5 to 80 cm(3) in size were imaged using contrast enhanced MRI with their arms in two positions. A thin-plate spline registration scheme was used to match these two configurations. The registration algorithm uses the surface markers only and does not employ the image intensities. Tumour outlines were segmented and centre of mass (COM) displacement and Dice measures of lesion overlap were calculated. The relationship between the number of markers used and the COM-displacement was also studied. The lesion COM-displacements ranged from 0.9  to 9.3 mm and the Dice overlap score ranged from 20% to 80%. The registration procedure took less than 1 min to run on a standard PC. Alignment of pre-surgical supine MR images to the patient using surface markers on the breast for co-registration therefore appears to be feasible.

Real-time virtual sonography (RVS)-guided vacuum-assisted breast biopsy for lesions initially detected with breast MRI

PURPOSE

To report on our initial experiences with a new method of real-time virtual sonography (RVS)-guided 11-gauge vacuum-assisted breast biopsy for lesions that were initially detected with breast MRI.

MATERIALS AND METHODS

RVS-guided 11-gauge vacuum-assisted biopsy is performed when a lesion with suspicious characteristics is initially detected with breast MRI and is occult on mammography, sonography, and physical examination. Live sonographic images were co-registered to the previously loaded second-look spine contrast-enhanced breast MRI volume data to correlate the sonography and MR images.

RESULTS

Six lesions were examined in six consecutive patients scheduled to undergo RVS-guided 11-gauge vacuum-assisted biopsy. One patient was removed from the study because of non-visualization of the lesion in the second-look spine contrast-enhanced breast MRI. Five patients with non-mass enhancement lesions were biopsied. The lesions ranged in size from 9 to 13 mm (mean 11 mm). The average procedural time, including the sonography and MR image co-registration time, was 25 min. All biopsies resulted in tissue retrieval. One was fibroadenomatous nodules, and those of four were fibrocystic changes. There were no complications during or after the procedures.

CONCLUSION

RVS-guided 11-gauge vacuum-assisted breast biopsies provide a safe and effective method for the examination of suspicious lesions initially detected with MRI.

Direct measurement of speed of sound in cartilage in situ using ultrasound and magnetic resonance images

This study verified the accuracy of the speed of sound (SOS) measured by the combination method, which calculates the ratio between the thickness values of cartilage measured by using the magnetic resonance imaging (MRI) and the ultrasonic pulse-echo imaging, and investigated in vivo application of this method. SOS specific to an ultrasound imaging device was used as a reference value to calculate the actual SOS from the ratio of cartilage thicknesses obtained from MR and ultrasound images. The accuracy of the thickness measurement was verified by comparing results obtained using MRI and a non-contact laser, and the accuracy of the calculated SOS was confirmed by comparing results of the pulse-echo and transmission methods in vitro. The difference between laser and MRI measurements was 0.05 ± 0.22 mm. SOS values in a human knee measured by the combination method in the medial and lateral femoral condyles were 1650 ± 79 and 1642 ± 78 m/s, respectively (p < 0.05). The results revealed the feasibility of in situ SOS measurement using the combination method.

PET/US fusion as a problem-solving tool in oncology imaging: differentiation of hernia repair mesh plugs from malignancy suspected on PET/CT

PET/CT is an established modality for evaluation of malignant disease. However, in many cases, specificity is impaired by false-positive findings. Recognition of these cases is crucial for correct diagnosis and subsequent patient management. In the presented case, malignant disease was suspected in a young man because of a history of B symptoms. F-FDG PET/CT showed hypermetabolic foci in both inguinal regions initially classified as possible lymphoma. Using a novel technique for PET/US fusion, ultrasound and PET were coregistered to clarify that PET hypermetabolism was due to a foreign body reaction after plug hernioplasty performed several years earlier.

Real-time image fusion involving diagnostic ultrasound

OBJECTIVE

The aim of our article is to give an overview of the current and future possibilities of real-time image fusion involving ultrasound. We present a review of the existing English-language peer-reviewed literature assessing this technique, which covers technical solutions (for ultrasound and endoscopic ultrasound), image fusion in several anatomic regions, and electromagnetic needle tracking.

CONCLUSION

The recent progress of real-time ultrasound in image fusion may provide several new possibilities, including diagnosis, treatment, and follow-up of oncologic patients.

Evaluation of the usefulness of breast CT imaging in delineating tumor extent and guiding surgical management: a prospective multi-institutional study

OBJECTIVE

The aim of the present study was to evaluate the usefulness of computed tomographic (CT) imaging in delineating tumor extent and guiding surgical management.

BACKGROUND

The routine use of preoperative magnetic resonance imaging (MRI) is a controversial issue in breast cancer management. Negative studies with regard to the utility of MRI might be due to differences in positioning during imaging and subsequent surgery.

METHODS

Candidates for breast-conserving surgery were eligible for the study. The surgeons marked the line of planned excision on the skin, which was also recorded on the CT image. Contrast-enhanced breast CT was performed in the supine surgical position. The CT results were used to help determine the extent of resection. The pathological findings were then compared with the CT-guided surgical plans.

RESULTS

A total of 297 patients were involved. The surgeons widened the extent of resection in 42 (14.1%, 95% confidence interval 10.1%-18.1%) patients on the basis of the CT findings. Among the 6 patients whose procedures were changed to mastectomy, 4 had pathologically multicentric tumors and 2 had widely spread intraductal components. The remaining 36 patients underwent quadrantectomy instead of wide excision on the basis of the CT images. There were 3 patients in whom conversion from wide excision to quadrantectomy resulted in overexcision. Preoperative breast CT may have reduced the positive margin rate and also correctly changed the extent of surgery in 13.1% of patients.

CONCLUSIONS

This prospective study suggests that breast CT, carried out in the supine position, is useful in the preoperative determination of the optimal surgical procedure.

Diagnostic imaging strategy for MDCT- or MRI-detected breast lesions: use of targeted sonography

BACKGROUND

Leading-edge technology such as magnetic resonance imaging (MRI) or computed tomography (CT) often reveals mammographically and ultrasonographically occult lesions. MRI is a well-documented, effective tool to evaluate these lesions; however, the detection rate of targeted sonography varies for MRI detected lesions, and its significance is not well established in diagnostic strategy of MRI detected lesions. We assessed the utility of targeted sonography for multidetector-row CT (MDCT)- or MRI-detected lesions in practice.

METHODS

We retrospectively reviewed 695 patients with newly diagnosed breast cancer who were candidates for breast conserving surgery and underwent MDCT or MRI in our hospital between January 2004 and March 2011. Targeted sonography was performed in all MDCT- or MRI-detected lesions followed by imaging-guided biopsy. Patient background, histopathology features and the sizes of the lesions were compared among benign, malignant and follow-up groups.

RESULTS

Of the 695 patients, 61 lesions in 56 patients were detected by MDCT or MRI. The MDCT- or MRI-detected lesions were identified by targeted sonography in 58 out of 61 lesions (95.1%). Patients with pathological diagnoses were significantly older and more likely to be postmenopausal than the follow-up patients. Pathological diagnosis proved to be benign in 20 cases and malignant in 25. The remaining 16 lesions have been followed up.Lesion size and shape were not significantly different among the benign, malignant and follow-up groups.

CONCLUSIONS

Approximately 95% of MDCT- or MRI-detected lesions were identified by targeted sonography, and nearly half of these lesions were pathologically proven malignancies in this study. Targeted sonography is a useful modality for MDCT- or MRI-detected breast lesions.

Real-time virtual sonography, a coordinated sonography and MRI system that uses magnetic navigation, improves the sonographic identification of enhancing lesions on breast MRI

This study verified that recently developed real-time virtual sonography (RVS) to coordinate a sonography image and the magnetic resonance imaging (MRI) multiplanar reconstruction (MPR) with magnetic navigation was useful. The purpose of this study was to evaluate the accuracy of RVS to sonographically identify enhancing lesions by breast MRI. Between December 2008 and May 2009, RVS was performed in 51 consecutive patients with 63 enhancing lesions. MRI was performed with the patients in the supine position using a 1.5-T imager with a body surface coil to achieve the same position as with sonography. To assess the accuracy of the RVS, the following three issues were analyzed: (i) The sonographic detection rate of enhancing lesions, (ii) the comparison of the tumor size measured by sonography and the MRI-MPR and (iii) the positioning errors as the distance from the actual sonographic position to the expected MRI position in 3-D. Among the 63 enhancing lesions, 42 (67%) lesions were identified by conventional B-mode, whereas the remaining 21 (33%) initial conventional B-mode occult lesions were identified by RVS alone. The sonographic size of the lesions detected by RVS alone was significantly smaller than that of lesions detected by conventional B-mode (p < 0.001). The mean tumor size provided by RVS was 12.3 mm for real-time sonography and 14.1 mm for MRI-MPR (r = 0.848, p < 0.001). The mean positioning errors for the transverse and sagittal planes and the depth from the skin were 7.7, 6.9 and 2.8 mm, respectively. The overall mean 3D positioning error was 12.0 mm. Our results suggest that RVS has good targeting accuracy to directly compare a sonographic image with MRI results without operator dependence.

Preoperative CT evaluation of intraductal spread of breast cancer and surgical treatment

It is always a challenge to accurately determine the appropriate extent of resection in breast-conserving surgery (BCS), in order to reduce the need for re-excision, prevent local recurrence, and optimize cosmetic results. Detecting intraductal spread alone with high sensitivity may not be enough to realize safe BCS. Computed tomography carried out with the patient in the supine position accompanied by adequate marking is effective for preoperative determination of the optimum extent of BCS.

Accuracy of magnetic resonance in suspicious breast lesions: a systematic quantitative review and meta-analysis

Dynamic contrast-enhanced breast magnetic resonance (MR) is a promising emerging technique for evaluating breast lesions. A quantitative systematic review was performed to estimate the accuracy of breast MR in the diagnosis of high-risk breast lesions and breast cancer. A comprehensive search of the Cochrane Library, MEDLINE, CANCERLIT, LILACS, and EMBASE databases was performed from January 1985 to August 2010. The medical subjects heading (MeSH) and text words for the terms "breast neoplasm", "breast lesions", "breast cancer" and "magnetic resonance" were combined with the MeSH term diagnosis ("sensitivity and specificity"). Studies that compared breast MR with paraffin-embedded sections parameters for the diagnosis of breast lesions (benign, high-risk borderline, and breast cancer) were included. Sixty-nine studies were analyzed, which included 9,298 women with 9,884 breast lesions. Interrater overall agreement between breast MR and paraffin section diagnosis was 79% (κ = 0.55), indicating moderate agreement. Pooled sensitivity and specificity were 90% [95% CI 88-92%] and 75% [95% CI 70-79%], respectively. The pooled likelihood positive ratio was 3.64 (95% CI 3.0-4.2) and the negative ratio was 0.12 (95% CI 0.09-0.15). For breast cancer or high-risk lesions versus benign lesions, the AUC was 0.91 for breast MR and the point Q* was 0.84. In summary, breast MR is a useful pre-operative test for predicting the diagnosis of breast lesions.

Real-time Virtual Sonography for navigation during targeted prostate biopsy using magnetic resonance imaging data

OBJECTIVES

To evaluate the effectiveness of the medical navigation technique, namely, Real-time Virtual Sonography (RVS), for targeted prostate biopsy.

METHODS

Eighty-five patients with suspected prostate cancer lesions using magnetic resonance imaging (MRI) were included in this study. All selected patients had at least one negative result on the previous transrectal biopsies. The acquired MRI volume data were loaded onto a personal computer installed with RVS software, which registers the volumes between MRI and real-time ultrasound data for real-time display. The registered MRI images were displayed adjacent to the ultrasonographic sagittal image on the same computer monitor. The suspected lesions on T2-weighted images were marked with a red circle. At first suspected lesions were biopsied transperineally under real-time navigation with RVS and then followed by the conventional transrectal and transperineal biopsy under spinal anesthesia.

RESULTS

The median age of the patients was 69 years (56-84 years), and the prostate-specific antigen level and prostate volume were 9.9 ng/mL (4.0-34.2) and 37.2 mL (18-141), respectively. Prostate cancer was detected in 52 patients (61%). The biopsy specimens obtained using RVS revealed 45/52 patients (87%) positive for prostate cancer. A total of 192 biopsy cores were obtained using RVS. Sixty-two of these (32%) were positive for prostate cancer, whereas conventional random biopsy revealed cancer only in 75/833 (9%) cores (P < 0.01).

CONCLUSIONS

Targeted prostate biopsy with RVS is very effective to diagnose lesions detected with MRI. This technique only requires additional computer and RVS software and thus is cost-effective. Therefore, RVS-guided prostate biopsy has great potential for better management of prostate cancer patients.